The present invention relates to an apparatus for binding sheets of paper, for example computer sheets, by using so-called hot-melt adhesive. The apparatus comprises a body provided with a handle, an adhesive container located within the body, heating means for maintaining the adhesive at the required proportioning temperature, as well as proportioning means.
In the prior art method presented in the Finnish Patent Application no 780 922 for binding sheets of paper, the sheets are bound by employing a cover made, for example, of cardboard. A thermoplastic layer of adhesiver material is located in the inside of the back of the cover. The layer is melted by heating so that it sticks the sheets to each other and to the cover. The aforesaid patent application also introduces a nozzle for producing the adhesive belt in the back of the cover. The nozzle is meant to be attached to a normal hot-melt unit. The melted adhesive is pumped from the hot melt to the unit nozzle. The temperature of the adhesive located in the nozzle is kept suitable by means of electric resistances and a thermostat placed in the nozzle. The proportioning of the adhesive takes place through a hole located in the nozzle. The form of the hole conforms to the cross-section of the adhesive layer desired in the back of the cardboard cover.
In the prior art, there are also known various portable pistols for spreading hot-melt adhesive. An example is the apparatus presented in the British Patent Publication no 1 517 821. All previously known proportioning means have one characteristic in common, namely the feature that the melted adhesive is pressed onto the desired working surface through a suitable nozzle.
The above described method for binding sheets by means of special covers has several drawbacks. According to the thickness of the bunch of sheets to be bound, it is necessary to have several covers with varying sizes. The use of covers involves certain costs irrespective of the width of the covers. The sticking of the sheets to the cover is not always complete because the cardboard cover is a good heat insulator and the hot-melt adhesive may not always melt in a manner so as to be sufficiently liquid in order to provide for a perfect agglutination result. Moreover, the cardboard covers are not always desirable, or even suitable.
The use of previously known hot-melt pistols is not recommended for binding sheets because by employing a pistol having a standard width it is extremely difficult to create an even layer of adhesive, exactly of the same width as the bunch of sheets to be bound. If the nozzle is narrower than the bunch of sheets, all sheets will not be bound firmly enough. If the nozzle is wider than the bunch of sheets, the adhesive spreads all over. In any case, it is practically impossible to guide the nozzle manually.